334 Prakt. Met. Sonderband 52 (2018) 
As the reaction influences matrix composition and properties [4], it is of great interest to ’ 
understand its formation kinetics as well as its general structure and composition. Hence, 
the influence of HIP time on the amount of reaction phase formed is investigated in this work. 
2. METHODOLOGY 
2.1 MMC Production and Preparation 
The matrix steel powder denoted as M7 was sourced from Nanoval (Germany) and has a 1 RESU 
dso of 19.9 ym. The nominal composition of M7 is given in Table 1. The TiC powder was 
sourced from Sigma Aldrich (Germany) and its dso number is = 2 ym. The carbon content of i16en% 
TiC was tested by combustion analysis and the stoichiometry was found to be TiCo.se7. 
Metallic impurities were tested by X-ray fluorescence analysis and only Fe (0.05 wt. %) and &18 
W (0.16 wt. %) were above the detection level of 0.01 wt.%. „le 
was 
Table 1. Nominal composition of the steel matrix powder M7 oo CR 
Febase |C [Si [Mn [Cr [Mo [V |W [Co Ta pu 
M7 [wt.%] | 0.46 0.57 042 [437 [2.06 0.63 1.60 468 % 7.08 
After weighing in M7 + 10 vol.% TiC, the powders were blended for 2 h in a tumble mixer. xe 8 
Subsequently, the powder blend was compacted by HIP approximately 1100 °C whereas fre 
samples with dwell times of 3.5, 6.0 and 24 h were produced. All samples were heat treated ‚Ümber, + 
after consolidation by austenitizing at 1140 °C for 20 min, quenching and three times 
tempering for 2 h. Sample surfaces were mechanically polished with 220, 500, 1200, 2400 
SiC paper before polishing with 3 um and 1 um diamond suspension. 
2.2 Experimental 
Scanning transmission electron microscopy coupled with energy dispersive spectroscopy 
(STEM/EDS) was conducted on a FEI TECNAI F20 equipped with an EDAX Apollo XLTW 
SDD EDS unit. STEM images were captured by a high-angle annular dark field (HAADF) 
detector. Foils were prepared by lift out technique [8] using a Zeiss Auriga 40 scanning 
electron microscope (SEM) and focused ion beam workstation. This device was also used 
for the SEM investigations. For the quantitative image analysis 10 kV acceleration voltage 
are used and contrast and brightness levels kept as constant as possible. Quantitative 
image analysis was conducted on an area of approximately 22 x 15 um by manually _ 
selecting reaction phase areas. To consider the varying amounts of TiC in the investigated - 
sample areas, the amount of reaction phase is normalized with respect to present TiC. The 
normalized reaction phase content farewm is defined as in Eq. 1, wherein Amimc and Aric are . 
the absolute phase areas of the reaction phase and the original TiC. respectively. Rn 
Aime resi 
f = ———*100 Eq. 1 Measural 
A, REM Aime tATc (Eq. 1) foes 
& TM 
X-ray diffraction (XRD) analyses were performed with a Bruker D8 Advance goniometer and his 
Cr Ka radiation. The consequent semi-quantitative phase analysis was conducted by big 
simultaneously fitting two Pseudo-Voigt functions in OriginPro 2017G to a TiC/reaction Bom 
phase doublet peak in the XRD spectra. The normalized reaction phase content from XRD lage 
experiments gixro is calculated according to Eq. 2, wherein /rimc and fic are the integrated ~~, ,..